Loop material for touch fastening

ABSTRACT

Lightweight, non-woven loop products for hook-and-loop fastening are disclosed, as are methods for making them and end products employing them. The products are non-woven webs of entangled fibers of substantial tenacity, the fibers forming both a sheet-form web body and hook-engageable, free-standing loops extending from the web body. The product is stretched and stabilized to produce spaced-apart loop clusters extending from a very thin web of taut fibers. In important cases a binder is added to stabilize the product in its stretched condition. An example of the loop product is produced by needle-punching a batt of staple fibers in multiple needle-punching operations, applying a foamed acrylic binder, and then stretching the needled batt and curing the binder with the batt stretched. Other forming techniques are disclosed and several novel articles and uses employing such loop products are described, such as for filters and fasteners.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of pending U.S. patentapplication Ser. No. 08/922,292, filed Sep. 3, 1997, and also is acontinuation-in-part of PCT Patent Application US98/18401, filed Sep. 3,1998 and designating the United States, published on Mar. 11, 1999 as WO99/11452.

BACKGROUND OF THE INVENTION

This invention relates to loop material, particularly to material to beengaged with hooking members to form a fastening, to its manufacture anduse, and to fasteners comprising such loop material.

In the production of woven and non-woven materials, it is common to formthe material as a continuous web that is subsequently spooled. In wovenand knit loop materials, loop-forming filaments or yarns are included inthe structure of a fabric to form upstanding loops for engaging hooks.As hook-and-loop fasteners find broader ranges of application,especially in inexpensive, disposable products, some forms of non-wovenmaterials have been suggested to serve as a loop material to reduce thecost and weight of the loop product while providing adequate closureperformance in terms of peel and shear strength. Nevertheless, cost ofthe loop component has remained a major factor limiting the extent ofuse of hook and loop fasteners.

To adequately perform as a loop component for touch fastening, the loopsof the material must be exposed for engagement with mating hooks.Unfortunately, compression of loop material during packaging andspooling tends to flatten standing loops. In the case of diapers, forinstance, it is desirable that the loops of the loop material providedfor diaper closure not remain flattened after the diaper is unfolded andready for use.

SUMMARY OF THE INVENTION

We have realized that non-woven fabrics constructed with certainstructural features are capable of functioning well for their intendedpurpose as hook-engageable loop fabrics, while providing particularadvantage in regard to expense of manufacture and other properties.

According to one aspect of the invention, a loop component of a hook andloop fastener is provided. The loop component has a nonwoven body offibers with a basis weight of less than about 4 ounces per square yard(preferably, less than about 2 ounces per square yard). The fibers forma sheet-form base containing taut sections of fiber extending within acommon plane between tightened knots of fibers, and a great multiplicityof loop formations dispersed across the base. Each loop formation has atrunk of fibers drawn together by taut fibers of the base and extendingfrom an associated knot in the common plane of the base, and multiplehook-engageable loops formed of fibers of the trunk and extending fromthe trunk for engagement by hooks of a mating component.

In some embodiments, the majority of fibers forming the trunks andhook-engageable loops are crimped.

In some embodiments, the knots of the base each correspond to anassociated previous penetration of the body of fibers by a needle. Thebody of fibers, in some such cases, may include crimped staple fibers.

In some loop components, the fibers comprising the trunks of the loopformations are secured together by a cured binder in interstices withinthe trunks. Preferably, the cured binder composes between about 20 and40 percent of the total weight of the body of fibers.

In some cases, the fibers comprising the trunks of the loop formationsare secured together by fused surface portions of at least some of thefibers comprising the trunks.

In some cases, the fibers comprising the trunks of the loop formationsare secured together by interlocking crimps of the fibers.

In some embodiments, at least some of the fibers comprising the trunksof the loop formations each have a thickness that undulates along theirlength.

For some applications, the loop component also includes a resilientlayer of foam laminated to the base of the body of fibers.

A layer of resin is, for some applications, laminated to the base of thebody of fibers. The resin layer may form hook projections shaped toengage the loops of the component, for instance.

Preferably, the hook-engageable loops extend to an average loop height,measured as the perpendicular distance from the sheet-form base, ofbetween about 0.020 and 0.060 inch, and the average loop height isbetween about 0.5 and 0.8 times the overall thickness of the body offibers (defined to include the sheet-form base and a majority of theloops).

The sheet-form base has, in presently preferred embodiments, betweenabout 50 and 1000 tightened knots per square inch of area, from whichhook-engageable loop formations extend.

In some preferred configurations, the body of fibers is generallycomposed of fibers having a tenacity of at least 2.8 grams per denier.

For some important applications, the loop component preferably has aGurley stiffness of less than about 300 milligrams.

By “hook-engageable” and similar terms used above and throughout thisspecification, we mean that the loop material defines openings of sizeadequate to receive the tip or head portion of a male fastener element(such as a hook-shape or mushroom-shape element, for instance) forforming a fastening, and that the openings are exposed and extended forengagement.

By the word “entanglements” we mean that the nodes at which amultiplicity of fibers are intertwined in the non-woven web. Theseentanglements may be relatively loose, as formed directly by a needlingprocess, for instance, or tightened after formation of theentanglements. By the word “knots” we mean entanglements that have beentightened by applying tension to their intertwined fibers in at leastone direction in the plane of the web, and remain in an at leastpartially tightened state.

By “stabilized”, we mean that the web is processed to generally maintainits planar dimensions. In other words, a web “stabilized” in a stretchedcondition will generally maintain its stretched dimensions and notsignificantly relax or stretch further under conditions of normal use.One way of “stabilizing” the web, for instance, is by solidifying binderat a significant proportion of its entanglements.

We have also realized that such loop fabrics as just described areadvantageously produced by employing certain manufacturing techniquesand methods.

According to another aspect of the invention, a method of forming a loopfastener component is provided. The method includes the steps of:

(1) providing a sheet-form mat of fibers;

(2) tensioning the base fiber by applying tension across the width ofthe mat, thereby forming a tensioned web; and

(3) stabilizing the web in its tensioned state.

The mat includes at least one base fiber of a length greater than thewidth of the mat and extending substantially across the mat, and loopfibers freely disposed within the mat. The tensioned web is formed bydiscrete, taut portions of base fiber extending between tightenedentanglements. Relative movement between portions of the base fiberduring tensioning draws together portions of the loop fibers to formupstanding, hook-engageable loops extending from the entanglementswithin the tensioned web. The stabilized web and loops have a combinedweight of less than about 4 ounces per square yard.

In some cases, the step of stabilizing includes solidifying a binderwithin the entanglements of the tensioned web.

Preferably, the step of tensioning increases the width of the mat by atleast 20 percent.

In some embodiments, the step of providing a sheet-form mat of fibersincludes continuously spinning the base fiber onto a supporting surfacein a predetermined, overlapping pattern. In some cases, a pulsating airjet is impinged against the base fiber under conditions which cause thefiber to assumed a crimped form as it is spun.

In some embodiments, the base fiber has a cross-sectional property, suchas thickness or cross-sectional area, that varies along its length.

According to another aspect of the invention, a method of forming a loopfastener component for hook-and-loop fastening includes stretching agenerally planar non-woven batt of entangled fibers by at least 20percent (preferably, at least 50 percent) in at least one direction inits plane, thereby producing a stretched web of weight less than about 4ounces per square yard and having a generally planar web body withhook-engageable loops extending therefrom. A substantial number offibers of the body are regionally taut in the plane of the web body as aresult of the stretching, and extend in different directions radiatingfrom bases of the loops. Afterwards, the web is stabilized in itsstretched condition.

Preferably, the batt is retained against shrinking in a perpendiculardirection within its plane during stretching.

In some embodiments, after stretching the batt in one direction the battis stretched by at least 20% in another, perpendicular direction. Insome other cases, the batt is simultaneously stretched by at least 20%in two perpendicular directions within the plane of the batt.

The stretching preferably causes the regionally taut fibers of the webbody to be trained about loop-forming fibers in the bases of the loops,the batt being stretched in a manner that the loop-forming fibers formfree-standing formations that extend from the plane of the web body,each formation containing multiple fibers and forming multiple,hook-engageable loops.

According to another aspect of the invention, a method of forming a loopfastener component for hook-and-loop fastening includes the steps of:

(1) providing a generally planar length of non-woven batt of entangledfibers, the batt having a thickness that varies across its width fromone longitudinal edge thereof to an opposite longitudinal edge thereof;

(2) stretching the batt widthwise, thereby increasing the width of thebatt by at least about 20 percent and producing a stretched web having agenerally planar web body with hook-engageable loops extending therefrom(a substantial number of fibers of the body being regionally taut in theplane of the web body, and extending in different directions radiatingfrom bases of the loops); and then

(3) stabilizing the web in its stretched condition. Advantageously, thestretching causes the thickness of the batt to become substantiallyuniform over its width.

Preferably, the stretched batt has weight less than about 4 ounces persquare yard.

In some preferred embodiments, the stretched batt has width at leastabout twice the width of the batt prior to stretching.

The invention can provide a very inexpensive loop product which can veryeffectively engage and retain hooks, such as in hook-and-loop fasteners.The loop product can be particularly useful in combination withextremely small, inexpensive molded hooks as fasteners for disposableproducts, such as diapers, medical devices or packaging. We have found,for instance, that the structure of the extended “loop trees” of thematerial, described below in more detail, helps to prevent permanentflattening of the loops and provides some advantageous crush resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged side view of a hook-and-loop fastener.

FIG. 2 is an enlarged plan view of a loop fastener product.

FIG. 2A is a plan view of a loop fastener product, enlarged 5OX andshowing the structure of the web; and FIG. 2B is a schematic view of thestructure shown in FIG. 2A.

FIG. 3A is a highly enlarged side view of the loop fastener product ofFIG. 2; FIG. 3B is a sketch of the structure in the foreground of FIG.3A; FIG. 3C is a highly enlarged plan view of a portion of the loopfastener product of FIG. 2.

FIG. 4A is an enlarged side view of a hook-and-loop product made byultrasonically welding a loop product to a hook product. FIG. 4Billustrates a two-sided fastener product formed with loops on one sideand hooks on the other.

FIG. 5 illustrates a machine and process for forming the product of FIG.4B.

FIG. 6 illustrates a loop material containing longitudinal fibers.

FIGS. 7A-7C sequentially illustrate the formation of a loop tree.

FIG. 8 is a top view of an apparatus for making a nonwoven fabric.

FIG. 9 is a side elevational view of the apparatus of FIG. 8.

FIG. 10 shows an alternative arrangement of the second needling stage ofthe apparatus of FIG. 9.

FIGS. 11 and 11A are plan and side views, respectively, of a batt ofneedled material after the second needling stage.

FIG. 12 is a schematic view of an apparatus for stretching andstabilizing a nonwoven material.

FIGS. 12A and 12B are enlarged views of area 12A in FIG. 12 under twodifferent conditions of operation.

FIG. 13 is a top view illustrating another process for forming astretched, entangled fiber batt.

FIG. 13A is a side view of the process illustrated in the left half ofFIG. 13.

FIGS. 14A-14C are transverse cross-sections through a fiber batt thatillustrate, sequentially, stretching of a batt of non-uniform thicknessslit from a needled batt.

FIG. 15 is an enlarged illustration of a fiber of varying cross-section.

FIG. 16 shows a stretched loop product laminated to a layer of compliantfoam.

DESCRIPTION OF EMBODIMENTS

Referring first to FIG. 1, a molded hook fastener product 10 is shownengaging the loops of a very thin loop product 12. The photograph isquite enlarged, as shown by the scale on the left side of thephotograph. The minor divisions of the scale each represent a length of{fraction (1/64)}th (0.0156) inch (0.40 mm). Hook product 10 is of theCFM-29 designation, available from Velcro U.S.A Inc. of Manchester,N.H., U.S.A., and has hooks of only 0.015 inch (0.38 mm) height.Referring also to FIGS. 2 and 2A, loop product 12, a feature of thepresent invention, is very thin (as evidenced by the scale of thephotographs and its lack of opacity) and has relatively free fibersforming loops extending from one side of a continuous, tangled mat offibers. In this and the following photographs all scale graduations,unless otherwise marked, are in 0.0156 ({fraction (1/64)}) inch (0.40mm) increments.

As shown in FIG. 2, and especially in FIG. 2A, a substantial number ofthe fibers of the mat of loop product 12 are taut (i.e., not slack,regionally straight), extending between knots 18 of the loop productfabric. The taut fibers have been pulled taught by stretching the mat oftangled fibers in at least one direction in the plane of the fabric mat.Preferably, the mat is held against shrinking in one direction as it isstretched in a second, perpendicular direction. More preferably, the matis simultaneously stretched in two perpendicular directions. Theindividual fibers of the mat follow no definite pattern as in a wovenproduct, but extend in various directions within the plane of the fabricmat. The loops that extend from the loop product are of the same fibersthat comprise the mat but extend beyond the general mass of the mat, outof the plane of the mat, generally from associated knots 18. The knotdensity of the sample shown in the photograph was determined to beapproximately 180 knots per square inch by counting the number ofvisible knots within a given square area. The knots themselves arefairly tight, made up of several monofilament fibers, and areinterconnected by the taut fibers seen running between them. In betweenknots, the thin fiber mat is not very dense and is sheer enough topermit images to be readily seen through it. For low cost application,the fabric preferably weighs less than about 2 ounces per square yard(68 grams per square meter).

In this particular embodiment, the fibers of the mat are held in theirtaut, straightened condition by a water-based, acrylic binder (notvisible in the photograph) applied to the side of the mat opposite theloops to bind the mat fibers in their taut condition to stabilize theareal dimensions of the fabric, and to secure the loops at theirassociated knots. The binder generally ranges between 20 and 40% of thetotal weight of the fabric and in the presently preferred embodimentsaccounts for about one third of the total product weight. The resultingfabric is dimensionally stable and strong enough to be suitable forfurther processing by standard fabric-handling techniques. The fabricalso has a slight stiffness, like a starched felt, which can bemitigated by softeners or mechanical working if desired.

The schematic view of FIG. 2B illustrates the structure of planar web12, as viewed from one face of the web. In this view, theloop-engageable loops extend out of the plane of the web, from one side.Web 12 is composed of a non-uniform distribution of entangled fibers,with relatively high concentrations of the fibers at the bases, B, ofcorresponding loop structures, and relatively lower concentrations ofthe fibers in regions, R, lying between loop bases, B. The relativelyhigh concentrations of fibers at bases B correspond to tightened fiberentanglements. As illustrated in this sketch, and visible in FIG. 2A, asubstantial number of the fibers in the regions, R, between loop basesare taut in the plane of the web, extending in different directionsradiating from loop bases, B. By “taut”, we mean that a large percentageof these inter-base fibers have no give or slack, such that they maytransmit an applied tensile force with little or no displacement. Webelieve that the taut fiber portions extending across the sparse regionsbetween loop bases account for some of the beneficial properties of theloop product, giving it a perceptibly high strength-to-weight ratio as afastener component.

Near the center of both FIG. 2A and FIG. 2B is a particularly visibleloop base B, from which taut fibers can be seen emanating in a radialpattern. Also note that there are some fibers which are wrapped at leastpartially about other fibers of the loop base. These wrapping fibers areso wrapped as the result of stretching, during which straighteningfibers encounter loop fibers extending through the planar web. As theweb is further stretched, the loop fibers provide obstructions aboutwhich the straightening web base fibers are trained as they aredisplaced within the web plane. Thus the bases, B, of the loopstructures contain both portions of the loop-forming fibers extendingboth in and out of the plane of the web, and trained portions of tautfibers lying generally only in the plane of the web. The trainedportions of the taut fibers within the loop bases therefore contribute,as the web is stretched, to the definition of the free-standing loopformations. When the web is stabilized by binder, for instance, thesebases B become relatively rigid nodes and, importantly, provideanchoring for their associated loop structures. Thus the stretched andstabilized web, in some respects, resembles a planar truss, with itstaut radiating fibers forming tensile members between base nodes. As thetaut fibers may be readily “bent” out of their plane as the web flexes,the structure retains an advantageously high flexibility while resistingelongation and shrinkage within its original plane.

The individual fibers of loop fabric 12 shown in FIG. 2 have low denierand substantial tenacity (i.e., tensile strength per unit diameter) towork with very small hooks such as those illustrated in FIG. 1. Fiberswith tenacity values of at least 2.8 grams per denier have been found toprovide good closure performance, and fibers with a tenacity of at least5 or more grams per denier (preferably even 8 or more grams per denier)are even more preferred in many instances. In general terms for aloop-limited closure, the higher the loop tenacity, the stronger theclosure. The fibers of fabric 12 of FIGS. 1 and 2 are 6 denier staplepolyester fibers (cut to four inch lengths) and as a result of themethod of the manufacture, are in a drawn, molecular oriented state,having been drawn with a draw ratio of at least 2:1 (i.e., to at leasttwice their original length) under cooling conditions that enablemolecular orientation to occur, to provide a fiber tenacity of about 3.6grams per denier. The fibers in this example are of round cross-sectionand are crimped at about 7.5 crimps per inch (3 crimps per cm). Suchfibers are available from E.I. Du Pont de Nemours & Co., Inc., inWilmington, Delaware under the designation T-3367 PE T-794W 6×4. Theloop fiber denier should be chosen with the hook size in mind, withlower denier fibers typically selected for use with smaller hooks. Forlow-cycle applications for use with larger hooks (and thereforepreferably larger diameter loop fibers), fibers of lower tenacity may beemployed.

As an alternative to round cross-section fibers, fibers of othercross-sections having angular surface aspects, e.g. fibers of pentagonor pentalobal cross-section, can enhance knot tightening for certainapplications. Regardless of the particular construction of theindividual fibers, they, are selected to have a surface character thatpermits slippage within the knot-forming entanglements during tighteningso as to enable stretching the batt without undue fiber breakage.

Referring to FIGS. 3A and 3B, the loops 14 of loop fabric 12 projectprimarily from one side of the fabric. The stabilizing binder, in thiscase, is applied to the other side. The loop product is extremely thinfor use with very small hooks. The product shown, for instance, workswell with hooks of about 0.015 inch (0.4 mm) height and has a loopheight h_(L) (i.e., the height of loops 14 from the near general surfaceof fiber mat 16) of about 0.055 inch (1.40 mm). The loop product has anoverall thickness, t, including a majority of the loops, of only about0.090 inch (2.3 mm). When measuring loop height in products without avisibly distinguishable upper mat surface, we define the near surface ofthe mat to be the lowest planar surface above about 80 percent of thetotal mass of fibers. The loops of the loop structures preferably varyin height for good engagement, and the average loop height (i.e., thedistance from the top of the loop to the near surface of the mat) shouldgenerally be at least about the height of the hooks with which the loopproduct is to be used, and preferably between 2 and 10 times the headheight of the hooks used for applications requiring good shear strength.Importantly, individual loops of the loop structures should be largeenough to accept the head of an individual hook. For fasteners which areprimarily loaded in peel, or by loads perpendicular to the plane of thebase, the loops may be up to 15 times the head height of the hooks. Forexample, for use with 0.015 inch (0.4 mm) CFM-29 hooks (which have ahead height of 0.006 inch or 0.15 mm), the average height h_(L) of theloops should be between about 0.012 and 0.060 inch (0.3 and 1.5 mm) forgood shear performance. For use with 0.097 inch (2.5 mm) CFM-24 hooks(which have a head height of 0.017 inch or 0.43 mm and are alsoavailable from Velcro U.S.A. Inc.), the average height of the loopsshould be at least 0.035 inch (0.89 mm) and may be as high as 0.250 inch(6.4 mm) for applications focusing on peel loading. For low cost,flexible loop fabrics, the average loop height should generally bebetween about 0.020 and 0.060 inch (0.5 and 1.5 mm), and should bebetween about 0.5 and 0.8 times the overall thickness, t, of the loopproduct.

As seen in FIGS. 3A and 3B, loops 14 extend from free-standing clustersof loop fibers extending from the fibrous mat 16. The clusters 20 whichhave several monofilament loops 14 extending from a common elongated,substantially vertical trunk 22 we call “loop trees”. Another example ofa “loop tree” is seen in FIG. 3C. Each loop tree 20 extends from acorresponding knot 18 in which the loops of the cluster are anchored.Interstices between individual filaments in the trunk portion 22 andbase of each tree, and in each knot 18, provide paths for the wicking ofliquid binder, under the influence of surface tension of the liquidbinder, to provide additional localized stiffness and strength. Thevertical stiffness of the trunk portion 22 of each tree, provided bothby the bundling of multiple trunk fibers by circumscribing fibers of thebase and by the cured binder, helps the trees to “stand proud”, orerect, to present their associated loops for engagement. This verticalstiffness acts to resist permanent crushing or flattening of the loopstructures, which can occur when the loop material is spooled or whenthe finished product to which the loop material is later joined iscompressed to be fit into packaging. Resiliency of the trunk portion 22,especially at its juncture with the base, enables trees that have been“toppled” by heavy crush loads to right themselves when the load isremoved. The trunk portions 22 should not be too stiff at theirinterface with the base of the loop material, otherwise the materialwould lose its soft hand and be less useful for garment applications.

Importantly, the density of clusters in the plan view is very low (FIGS.2 and 2A), leaving sufficient room between the “branches” of neighboringtrees to accommodate hooks and deflected loop material duringengagement. By leaving adequate room between neighboring loop trees, theheads of many of the hooks of a mating material extend down to the baseof the loop material during engagement, without flattening the loopstructures. This high penetration rate helps to provide a highengagement rate as the penetrating hooks grab loops as a result of verysmall relative shear motion between the hooks and the loops while theloop forest is thus penetrated.

Accumulations of solidified binder 21 can be seen in the knots in thehighly magnified plan view of FIG. 3C. Applied in liquid form in thisexample, preferably before the knots are tightened, the bindercontributes to securing the loops against being pulled out of the web.

Referring back to FIG. 1, with proper clearance between loops for theaccommodation of hooks, the fully engaged fastener (i.e., the loopproduct and mating hook product together) has an overall thickness ofonly the sum of the thickness of the hook product (including hooks) andthe “ground” portion of the loop product (i.e., the thickness of the mat16 between loop clusters, FIG. 3B). In other words, the free standingloops of the loop product do not add to the thickness of the completedfastener. Because of the ultra-thin ground portion 16 of the loopproduct disclosed herein (see FIG. 3B), the combination of loop product12 with mating hook product 10 provides a fastening of very smallthickness. For example, the engaged fastener of FIG. 1 has an overallthickness of only about 0.050 inch (1.3 mm; thinner, in this case, thanthe overall thickness of the unengaged loop product, as the taller loopclusters are somewhat compressed by the hook product engaged withshorter loop clusters).

In addition to being advantageously thin, loop fabric formed accordingto the new principles is particularly flexible. Flexibility can be veryimportant in some fastener applications, especially when the fastenermust flex during use, as when used on an article of apparel. In suchinstances, the loop product of the invention should have a bendingstiffness of less than about 300 milligrams, preferably less than about100 milligrams, as measured with a Gurley stiffness tester. More detailson the use of Gurley stiffness testers can be found in Method T 543OM-94, published in 1984 by the Technical Association of Pulp and Paper(TAPPI).

Various synthetic or natural fibers may be employed in the invention. Insome applications, wool and cotton may provide sufficient fiberstrength. Presently, thermoplastic staple fibers which have substantialtenacity are preferred for making thin, low-cost loop product that hasgood closure performance when paired with very small molded hooks. Forexample, polyolefins (e.g., polypropylene or polyethylene), polyesters(e.g., polyethylene terephthalate), polyamides (e.g., nylon), acrylicsand mixtures, alloys, copolymers and coextrusions thereof are suitable.Polyester is presently preferred.

For a product having some electrical conductivity, a small percentage ofmetal fibers may be added. For instance, loop products of up to about 5to 10 percent fine metal fiber, for example, may be advantageouslyemployed for grounding or other electrical applications.

Various binders may be employed to stabilize the fabric. By “binder” wemean a material within the mat (other than the fibers forming the mainfastener loops) that secures the loop fibers at associated knots. Insome applications, the binder is an adhesive. In other applications, thebinder is in the form of fibers of low-melt polymer dispersed throughoutand entangled within the fabric. These low-melt fibers are melted to wetthe knot-forming entanglements and then cooled and solidified to securethe loops and stabilize the fabric. The binder preferably fullypenetrates and permeates the interstices between individual fibers inthe entanglements of the mat. When employing a liquid binder, the binderis preferably selected to have a sufficiently low viscosity and surfacetension to enable it to flow into the untightened (or tightening)entanglements. In the embodiments in which the entanglements aresubsequently tightened (such as the loop product shown in FIG. 2), thisselected distribution of the fluid binder helps to secure the knots withminimal stiffening of the overall product and without requiringsubstantial amounts of binder.

In any event, the amount and penetration of the binder should beselected to avoid substantial interference with the desiredhook-engaging function of the loops while adequately stabilizing the matand securing the loops against being pulled from their associatedentanglements. For use in applications in which the loop product maycome in direct contact with sensitive skin, such as in diapers, theamount and type of binder should also be selected to be biocompatible toavoid skin irritation. Formaldehyde-free binders, for instance, arepreferred. As irritation can be aggravated by stiffness, preferably onlyenough binder to perform the above functions is applied. In someapplications, for instance those in which the loop product is directlyadhered to a supporting fabric and which does not require substantialfastener strength, the loop product may be provided without a binder.

In important instances, the binder also includes an organic or inorganicfire-retardant, such as antimony oxide, zinc borate, aluminum trihydrateor decabromobiphenyl oxide.

The specific loop product 12 of FIGS. 1 and 2 includes about one thirdby weight water-based acrylic binder produced by mixing 80 parts“NACRYLIC” X-4280, a self-reactive acrylic emulsion, with 20 parts“X-LINK” 2804, a self-crosslinking, polyvinyl acetate/acrylate emulsion,both available from National Starch and Resin Company in Bridgewater,N.J. As produced, loop product 12 substantially consists only of thedrawn fibers of the thin mat, some of which extend out of the mat toform loops, and the binder. Without any additional backing or laminate,it is strong enough to be handled as a fabric material, and may beapplied to surfaces as a closure member by sewing, ultrasonic welding,adhesive, radio frequency welding, or other known attachment means. FIG.4A, for instance, shows a hook-and-loop product 22 formed byultrasonically welding a piece of the loop material 12 of FIG. 2 to apiece of CFM-29 hook product. The resulting product 22 can be formedinto a closed band by engaging its loops with its hooks.

Referring to FIG. 6, another loop fabric material 26 includes, inaddition to the drawn, molecularly oriented, randomly laid fiberspreviously described, continuous robust longitudinal monofilament fibers28 extending substantially in one direction to augment the tensilestrength of the finished fabric in the direction of the strands. Forthis purpose the diameter of the longitudinal monofilaments is selectedto be larger than the barbs of the needles to reduce engagement of themonofilaments by the needles during the needling process. Monofilaments28 are preferably crimped to enable them to be stretched a limitedamount in the machine direction as the fabric is stretched before beingstabilized. Alternatively, a stretchable scrim of similarly large fibersor film may be incorporated into the web of fibers to increase tensilestrength in both longitudinal and lateral directions.

FIG. 4B illustrates a one-piece fastener product consisting of alamination of the above-described loop material and molded hook tape.Product 300 has a base 302 with integrally molded hooks 304 projectingfrom one side and the above-described non-woven loop material 12 securedto the other side. At the interface 306 between the two layers theplastic from base 302 flows around and entraps some of the fibers of thebase web of loop material 12, encapsulating one face of the web inthermoplastic material to form a permanent laminate of the two layers.Because of the extremely light nature of the non-woven material of theinvention, care must be taken to only encapsulate the web and to leavethe functional loops exposed for engagement with hooks 304. Theproperties of the non-woven material, the viscosity of the plastic andthe pressure in the nip (see FIG. 5) will determine the degree to whichthe plastic flows into the fibrous network, or put alternately, thedegree to which the non-woven will imbed into the plastic. The resultinglaminated product is particularly thin and flexible, due in part to thethinness of the loop material.

The product of FIG. 4B may be economically formed by the process andapparatus illustrated in FIG. 5. Extruder barrel 308 melts and forcesthe molten plastic 310 through die 312 into the nip 314 between baseroller 316 and cavity roller 318 containing cavities to form the hooksof a strip fastener of the well known hook and loop type. The stripfastener material formed in nip 314 travels around the periphery ofcavity roller 318 and around stripping roller 320, which assists inpulling the finished product 300 from the cavity roll, and from there toa windup device, not shown.

While many methods of feeding sheet material to the forming section ofthe hook forming device are possible, FIG. 5 illustrates a deviceparticularly well adapted to that purpose. By introducing loop material12 into nip 314 at the same time molten plastic 310 is forced into thenip, the loop material will bond intimately with the fastener to becomean integral part of the structure of the strip fastener. Optionally, aset of pins 322 at the edges and around the periphery of backing roller316 carry the loop material 12 into nip 6 in a flat, unwrinkled state.To assure proper tensioning and alignment of the secondary sheetmaterial, a roll 324 of loop material 12 is mounted on a let off deviceand threaded around diversion roller 326 into a web straightening device328, well known in the art as typically sold by the Fife ManufacturingCompany which assures that the web of loop material is centered as it isfed onto backing roller 316 around scroll roll 330, which has ribs ofelastomeric material to firmly grip the sheet and impinge it againstbacking roller 316 and onto pins 322. Pins 322 and roller 316 deliverthe web into nip 314 along with molten plastic 310. As molten plastic310 is forced by the pressure imposed upon it by the narrow space of nip314, it flows into cavities in cavity roller 318 and also into pores inthe adjacent face of the loop material being carried by backing roller316. In this way the loop material is intimately joined to the base ofthe forming hook fastener tape to form laminated product 300.

For more detail about proper operation of the apparatus of FIG. 5, thereader is referred to U.S. Pat. No. 5,260,015 to Kennedy, et al., whichdiscloses laminates made with heavier loop materials.

The very low thickness and stiffness of the above-described loopmaterial, along with its low cost and good closure performance, make itparticularly useful for many touch fastener and filtering applications.Many examples of such uses are described in co-pending U.S. patentapplication Ser. No. 08/922,292, the disclosure of which is incorporatedherein by reference as if fully set forth.

One of the underlying principles embodied in the formation ofself-erecting loop trees is that pulling on a tangled bunch of fiberswill form knots. This phenomenon is true with regard to continuousfibers (as any fisherman knows) as well as to bunches of short fiberstangled sufficiently to form a coherent mass. Simply stretching atangled mass of fibers is insufficient to form an adequate number oferect loop trees, however. The formation of an erect structure of theproper height, as shown in FIG. 3A for instance, involves the tighteningof adjacent fibers within the plane of the base of the mat aboutmultiple tree-forming fibers at two spaced-apart points along eachtree-forming fiber, which themselves remain untightened between suchspaced-apart points.

FIGS. 7A-7C illustrate this tree-forming sequence. For clarity, only onetree-forming fiber 400 is shown (in bold for distinction), and only twotightening base fibers 402 are shown. Preferably, an average of at leastthree or four tree-forming fibers will be drawn together at any givenknot to form a single trunk. Referring first to FIG. 7A, all fibers areinitially slack. As the fibers are pulled taut (FIG. 7B), fibers 402tighten about fiber 400, drawing together spaced-apart points 400 a and400 b into a tight entanglement 404 at the base of the loop structure406 formed by the segment of fiber 400 between points 400 a and 400 b.The wicking of binder 408 into the interstices between fibers in knot404 (FIG. 7C) adds rigidity to the trunk of the structure and itsconnection to the base. Again, with multiple tree-forming fibers 400drawn together at a common entanglement 404, this process forms astanding loop tree with multiple extended loops.

FIGS. 8 and 9 illustrate one apparatus and method for producing theabove-described loop material. The apparatus includes a feeder 110(with, e.g., bale breakers, blender boxes or feed boxes), which feedsstaple fibers of a desired length of drawn fibers to carding machines112. The carding machines 112 card the staple fibers to produce cardedwebs of fibers 114 which are picked up by the take-off aprons 116 ofcross-lappers 120. The cross-lappers 120 also have lapper aprons 118which traverse a floor apron 122 in a reciprocating motion. Thecross-lappers lay carded webs 114 of, for example, about 12 to 18 inches(30 to 45 cm) width and about one inch (2.5 cm) thickness on the floorapron 122, to build up several thicknesses of criss-crossed web to forma batt 124 of, for instance, about 90 to 120 inches (2.3 to 3.0 m) inwidth and about 4 inches (10 cm) in thickness. During carding, thematerial is stretched and pulled into a cloth-like mat consistingprimarily of parallel fibers. With nearly all of its fibers extending inthe carding direction, the mat has some strength when pulled in thecarding direction but almost no strength when pulled in the cardingcross direction, as cross direction strength results only from a fewentanglements between fibers. It is important to note that the cardingdirection is not the machine direction of the finished product. Duringcrosslapping, the carded fiber mat is laid in an overlapping zigzagpattern, creating batt 124 of multiple layers of alternating diagonalfibers. The diagonal layers, which extend in the carding crossdirection, extend more across apron 122 than they extend along itslength. For instance, we have used batt which has been crosslapped toform layers extending at anywhere from about 6 to 18 degrees from thecross direction of the finished product. The resultant crosslapped batt124, therefore, has more cross direction strength (i.e., across apron122) than it has machine direction strength (i.e., along apron 122).Note that the machine direction of the final product is in the samesense as the direction along apron 122. Batt 124 has little machinedirection strength because the fiber layers are merely laid upon oneanother and are in no way woven together. The material properties andthe manufacturing process can be affected by the crosslapping angle. Asteeper angle may balance the cross and machine direction strengths,which may affect fastener performance and the ease of manufacturing.With more machine-directional crosslapping, in some cases the initialmachine direction stretch described below may be eliminated while stillobtaining a useful product.

In preparation for needling, batt 124 is gradually compressed in atapered nip between floor apron 122 and a moving overhead apron 138 toreduce its thickness to about one inch. A relatively thin, low densitybatt can thus be produced.

Needling of batt 124 is performed in multiple, sequential needlingstages in order to provide a very high density of needle penetrationswithout destroying the low density batt. In the presently preferredmethod felting needles are employed having fiber-engaging barbs on theirsides. Needle punching gives the batt cohesion. The needle barbs pullfibers from one layer of the batt through other layers, entangling thefibers from different layers that are oriented in different directions.The resulting entanglements hold the batt together.

From floor apron 122, the batt is passed to a first needle loom 140 withtwo needling stations 142 and 144 having rows of notched (i.e., barbed)needles. Needling station 142 needles the batt of staple fibers from itsupper surface at a density in the range of 100 to 160 punches per squareinch (15 to 25 per square cm). In this embodiment, the batt was needledat a density of 134 punches per square inch (21 per square cm).Subsequently, needling station 144 needles the once-needled batt asecond time, with needles which penetrate the batt from its uppersurface at a density in the range of 500 to 900 punches per square inch(78 to 140 per square cm) to produce a needled batt 146. In thisexample, the second needling is at a density of 716 punches per squareinch (111 per square cm). We refer to the operation of loom 140 as thefirst needling stage. Additional information on needling processes canbe obtained from the Association of the Nonwoven Fabrics Industry (INDA)of Cary, North Carolina, which publishes the INDA Nonwovens Handbook.

After the first needling stage, needled batt 146 is passed between driverolls 148 and into a J-box accumulator 150 which, besides holding a bankof batt to accommodate variations in processing rates, allows theneedled batt to relax and cool before entering the second needlingstage. Alternatively, the needled batt 146 may be spooled after thefirst needling stage, with subsequent operations performed on a secondline. If materials and conditions allow, the needled batt may be passeddirectly from the first needling stage to the second needling stagewithout accumulation, but care should be taken to ensure that the battis sufficiently cool and relaxed to withstand the second needling stage.

As a result of the needle punching, the fibers of the batt become highlyrandomized and chaotic. However, the underlying pattern of alternatingdiagonals remains unchanged, although obscured.

From J-box accumulator 150, needled batt 146 is pulled through aguider/spreader 152 (of, e.g., the one-over-two configuration) toproperly apply light tension to the batt as is customary for needling,without significant stretching of the batt. It then passes through asecond needle loom 154 for a second needling stage. The operation ofthis second stage is referred to “super needling”, as it is a very densesecondary needling operation and produces many loops of substantialloft. Loom 154 has a single needling station 156 in which needled batt146 is needled from the lower side to produce high-loft loops extendingfrom the upper side. To produce such loops, the sharp tips of thenotched needles of loom 154 are extended a substantial distance (e.g.,about ¼ inch or 6.3 mm) beyond the thickness of the batt in the oppositedirection as the needles of the first needling station, pushingindividual fibers away from the bulk of the batt to form upstandingloops. When the needles retract, the loops remain. The loops may beformed of fibers which originally lay on the opposite side of the batt,or from fibers drawn from the middle of the batt. In either case, theneedles drag fibers out of the batt and leave them extending from thebulk of the batt as loops which give one side of the super-needled batta fuzzy appearance.

This super-needling process does not require special needling bedplatesor supporting brushes into which the needles extend, such as areemployed in structured or random velour looms, although such techniquesmay be employed to advantage, e.g., where large loops are desired foruse with large hooks. The super-needling is primarily characterized asan extremely dense needling, on the order of about 1000 to 2000 punchesper square inch (155 to 310 per square cm), or preferably about 1400punches per square inch (217 per square cm). Standard barbed needles areemployed, such as triangular section 15×18×42×3 C222 G3017 feltingneedles from Groz-Beckert. During this secondary needling operation,individual fibers of the batt are pushed through the loop side of thebatt to produce loose, relatively lofty loops. Together, these loopsgive the loop side of the super-needled batt a fuzzy appearance andfeel. Too much extension of the individual loop fibers at this point cancause them to break during subsequent stretching, so the distance theneedles extend through the batt is selected in consideration of thedenier and tenacity of the fibers used. We have found that extending theneedles about ¼ inch (6.3 mm) beyond the batt works well for 6 denierfibers with a tenacity of about 3.5 grams per denier.

In one embodiment, illustrated in FIG. 10, needle loom 154 has anadditional, second needling station 158. After producing high-loft loopsextending from one surface, the batt is super needled in the otherdirection to produce loops extending from its other surface, such thatboth sides have extended loops.

After leaving loom 154, super-needled batt 160 is split into two running45 inch (114 cm) widths and spooled on rolls 162. As shown in FIG. 11,the fibers of batt 160 have been entangled by the needle punchingprocess to create loose entanglements throughout the batt. At thisstage, the batt is not an acceptable loop product for many hook-and-loopfastening applications, as the individual loops may be relatively easilypulled away from the batt and are not well anchored at theentanglements.

After super-needling, the loop definition, see FIG. 11A, on the workingside of the batt is also not as distinct as it can be after thestretching that is employed to produce products with loop trees. Thisstructural difference can be seen by comparing FIGS. 11, 11A with FIGS.2 and 3, for instance.

In another embodiment (not illustrated), the second needling stage isomitted. Instead, needle looms 142 and 144 of the first needling stage(FIG. 9) are configured to super-needle the batt in both directions.Loom 142 needles the batt from the top at a rate of 254 punches persquare inch (39 per square cm), with the needles penetrating the battand extending through the bottom of the batt a distance of 10.2millimeters. Loom 144 then needles the batt from the bottom at a rate of254 punches per square inch (39 per square cm), with the needlespenetrating the batt and extending through the top of the batt adistance of 7.1 millimeters to form loops on the top side of the batt.The needles of loom 144 tend to take fibers that have been pushedthrough the bottom of the batt by the needles of loom 142 and force themback up through the batt in the formation of topside loops. Althoughthis process results in a relatively small number of loops on the bottomof the finished product, due to the first needling of loom 142, theresulting product has been found to be useful for some applications. Theneedling density, speed, and penetration of looms 142 and 144 may bevaried to produce a product with substantially no backside loops, orwith hook-engageable loops extending from both sides.

The batt following super needling has a fair amount of loft andresiliency, with the loops and other fibers of the batt forming loose,gentle arches between entanglements. At this point the batt is veryflexible, and the density of fibers gradually decreases away from eitherside of the material. At first glance, it can be difficult to tell whichside has been super-needled, if only one side has been subjected to thataction. Batt 160, in this example, has an overall thickness, includingloops, of about {fraction (3/16)} inch (4.8 mm) and a weight of betweenabout 2 and 4 ounces per square yard (68 and 135 grams per squaremeter).

Referring to FIG. 12, a spooled length of super-needled batt 160 isspooled from roll 162 by drive rolls 165 and into a J-box accumulator166, allowing roll 162 to be replaced and the batt spliced withoutinterrupting further processes. The J-box also allows the batt torecover from any elastic deformation caused by the spooling process.Batt 160 is pulled from accumulator 166 through a guider 168 to centerthe batt in the cross-machine direction. Guider 168 includes three rollsin a two-over-one configuration. The first and second rolls 170 and 172have left and right herringbone pattern scroll surfaces originating atthe center of the roll that, being slightly overdriven, urge anywrinkles in the batt toward its edges to remove them. The third roll,roll 174, is a split braking roll to controllably tension either half ofthe batt to guide the fabric to the left or right as desired.

From guider 168 the batt passes through a tension controller 176 thatmaintains a desired tension in the batt through the subsequent binderapplication process. Controlling the difference between the speed oftension controller 176 and downstream drive rolls 202 applies a desiredamount of machine direction stretch to the batt prior to cross-machinestretching. In some cases, no substantial machine direction stretch ispurposefully applied, any noted machine direction lengthening being dueonly to minimal web processing tension in the supply batt. In othercases, machine direction stretch is purposefully induced by runningdrive rolls 202 faster than tension controller 176.

In the embodiment in which batt 160 has been super-needled to produceloops extending from only its front side 188, batt 160 is next passedthrough a coating station 190 in which a foamed, water-based adhesive192 (i.e., a water-based adhesive, whipped to entrain air) is applied tothe back side 194 of the batt across its width.

Referring also to FIGS. 12A and 12B, the foamed liquid adhesive ispumped at a controlled rate through a long, narrow aperture 196 in theupper, surface of the applicator 198 as the batt is wiped across theaperture, thereby causing the adhesive to partially penetrate thethickness of the batt. Positioning bars 200, on either side of aperture196, are raised (FIG. 12A) and lowered (FIG. 12B) to control the amountof pressure between batt 160 and applicator 198. The depth ofpenetration of the adhesive into the batt is controlled (e.g., by theflow rate and consistency of adhesive 192, the speed of batt 160 and theposition of bars 200) to sufficiently coat or penetrate enough of thefiber entanglements to hold the product in its final form, whileavoiding the application of adhesive 192 to the loop-forming fiberportions of the front side 188 of the batt. The foaming of the liquidadhesive before application helps to produce an even coating of the backside of the batt and helps to limit penetration of the fluid adhesiveinto the batt. After the semi-stable foam is applied it has aconsistency similar to heavy cream, but the bubbles quickly burst toleave a liquid coating that flows as a result of wetting and surfacetension, into the tightening fiber entanglements. Alternatively, thefoam may have a thicker consistency, more like shaving cream, to furtherreduce the penetration into the batt and form more of a distinctresinous backing. A non-collapsible (i.e., stable) foam of urethane oracrylic, for instance, is useful to produce a radio frequency-weldablebacking which functions as a water barrier. Such a product hasparticular application to disposable garments and diapers.

It is important that the binder (e.g., adhesive 192) not interfere withthe loop-forming portions of the fibers on the front side 188 of thebatt. It is not necessary that the knot bases be completely covered bybinder; it is sufficient that they be secured by the binder in thefinished product to stabilize the fabric against significant furtherstretching and to strengthen the bases of the loops. Preferably, thebinder is at least partially in liquid form to wick into theentanglements before and while they are subsequently tightened duringstretching. The capillary action of the liquid binder is such thatexamination of the finished product shows that the binder is almostexclusively at the knots of the web (at the base of the loops, forinstance), and therefore does not tend to adversely affect either thefunctionality of the free-standing loops or the flexibility of the web.

After leaving coating station 190, the material is subjected tostretching in the plane of the web. In the presently preferred case theweb is wound through variable speed drive rolls 202 and onto a tenterframe 204 for cross-machine stretching (i.e., stretching in thecross-machine direction). The speed of drive rolls 202 is adjustable,with respect to both tension control 176 and the rails 206 of the tenterframe, to cause a predetermined amount of machine direction stretch inthe batt, either between tension control 176 and drive rolls 202, orbetween drive rolls 202 and frame rails 206, or both. In someembodiments no permanent machine direction stretch is applied, but thebatt is nevertheless held in tension to control adhesive penetration andmaintain proper frame rail pin spacing. In other embodiments the batt isgenerally stretched, in total, between about 20 percent and 50 percentin the machine direction before tentering.

As it enters tenter frame 204, the 45 inch wide batt 160 is engagedalong its edges by pins of frame rails 206 that maintain themachine-direction dimension of the material as it is stretched in thecross-machine direction. The spacing (of, e.g., about {fraction (3/16)}inch or 4.8 mm) between adjacent pins is maintained throughout thelength of the tenter frame, such that no additional machine-directionstretch is applied. Due to the needling, batt 160 should have enoughtensile strength to be properly engaged by the rail pins and withstandthe subsequent cross-machine stretching.

Tenter frame 204 has a tapered section where the rails 206 separate at aconstant, adjustable range rate over a machine-direction length of about10 feet (3 meters) to a final width which can range from 45 inches (114cm) to about 65 to 69 inches (165 to 175 cm). This equates to across-machine stretch, in this particular embodiment, of about 50percent. In general, to take advantage of the economics that can berealized according to the invention, the batt should be stretched toincrease its area by at least about 20 percent (we call this “percentareal stretch”), preferably more than about 60 percent areal stretch andmore preferably more than about 100 percent areal stretch, to increasethe area of the product while tightening the binder-containingentanglements of the batt that contribute to improvement in the strengthof anchorage of the individual loops. We have found that in some casesthe super-needled batt can be stretched, by employing the above method,at least 130 areal percent or more and provide very useful hook-engagingproperties. The more the stretch, the greater the overall yield and thelighter in weight the final product. Even greater overall cross-machinestretch percentages can be employed, for instance by using multipletentering stages in situations wherein the batt is constructed towithstand the stretch and still be able to reasonably engage hooks. Inone instance, the super-needled batt described above was stretched froman initial width of 45 inches (114 cm) to 65 inches (165 cm), softened(by adding a softener), slit to a 45 inch (114 cm) width, stretched asecond time to a 65 inch (165 cm) width before applying a binder, andstill had useful, hook-engageable loops. In some cases final productwidths of 6 to 8 feet (1.8 to 2.4 meters) or even much more can beachieved.

In one embodiment, the non-woven web starting material used tomanufacture the loop component is a fairly dense, needle punched,non-woven web of fibers lying in an apparently chaotic and tangledmanner. One side, the “fuzzy side”, has an excess of large, loose loopfibers created during a second needle punching process. The web is firststretched to 130 percent of its initial length in the machine direction.This stretching results in necking—the material narrows to 80 percent ofits initial width, from 45 inches (114 cm) to 36 inches (91 cm). It isthen coated with a binder. Next, it is stretched to 175% of its neckedwidth, from 36 inches (91 cm) to 63 inches (160 cm). During this processthe material becomes much more sparse, with spider-like clusters offiber (see bases B of FIG. 2B) serving to anchor the loop. The mechanismby which this change occurs relates to the method by whichinitial/non-woven web is manufactured.

Referring to FIG. 14A, a cross-lapped and needled batt 420 generally hasa smaller thickness (t_(m)) along its centerline than at itslongitudinal edges (t_(e)), due to the interrelation of motions ofconveyor, carded webs and cross-lappers during cross-lapping, which tendto create thicker batt edges (i.e., edges having a greater basis weightthan the center of the batt). The edge thickness may be 30% or moregreater than the mid-thickness, and the basis weight of the battgenerally varies across its width in proportion to its thickness.

By taking such a variable-thickness batt, slitting it down itscenterline into two widths 421 (of, for instance, 45 inches each inwidth), one of which is shown in FIG. 14B, and then stretching eachwidth 421 to a final width about equal to the width of the originalneedled batt, as shown in FIG. 14C, a useful loop product of uniformthickness is formed. The variation in thickness across the width of theslit batt is diminished as it is stretched, such that the finalstretched web thickness (t_(s)) is substantially uniform across thewidth of the finished product. We believe that the mechanism for thisthickness equalization is that the base fibers of the thinner regions ofthe batt are tightened first, thinning the thinner regions all the more,and then, when further stretching of the thinner regions is limited bytheir tightened fibers, the thicker regions are stretched until a matrixof taut fiber portions is formed within them as well. In effect, thematerial is “drawn” in the cross-machine direction, as tensioning beginsin the thinner areas of the batt and migrates or propagates to andthrough the thicker areas. We have found that the distribution of loopstructures across the width of the finished product is substantiallyuniform, even when starting with an uneven batt.

The amount of needling, the starting basis weight, and thestretchability of the batt are all related. Within a range of basisweight and needling density useful for creating a stretchable web,increasing either the basis weight of the starting batt or the needlingdensity will decrease the amount of stretch that can be applied to theneedled batt. As is known in the art, there is a minimum basis weightrequired for effective needling, below which an insufficient number ofentanglements will be formed by the needling to produce a coherent webwhich can be handled without falling apart. At the other end of thespectrum, too high of a basis weight can result in needle breakageand/or fiber breakage during needling. To produce the very light, thinloop material enabled by the invention, the basis weight of the startingbatt and the needling density should be selected to permit a fair amountof stretch of the needled material, as it is the stretching that thinsthe needled product and increases its yield. In other words, if theneedled product is to be stretched, the needling process should leave asubstantial proportion of the base fibers slack, and their entanglementsloose.

When loop material formed of a highly diagonal crosslapped batt isstretched in the machine direction, it is observed that little tensionis placed upon the constituent fibers. This is because the vast majorityof the fibers run in a diagonal direction that lies close to the crossmachine direction. Applying machine direction tension tends to increasethe angles at which the diagonals lie (i.e., move them toward a 45degree angle with the machine direction). They become steeper, or areturned to a degree toward the machine direction, much like the angles ofthe legs on a folding chair grow steeper when the chair is opened. Andjust as the leg base of a folding chair gets narrower as the chair getstaller, so does the material tend to neck and lose width as it isstretched. This is evidenced by breaking a piece of such material in themachine direction: the fibers do not break, they merely pull apart fromeach other. Because little tension is put on the fibers until they arenearly parallel, a mere 30 percent stretch does not disturb the chaoticarrangement of the fibers and little change can be seen under themicroscope. Even though the fibers are re-orienting, the arrangementlooks no less chaotic, since the fibers themselves are never broughtunder enough tension to straighten them out.

The second stretch of the above embodiment, performed in the crossmachine direction, produces drastic changes. Though somewhat more angledas a result of the first stretch, the fibers still extend more in thecross machine direction than in the machine direction. The fact that thefibers are oriented closer to cross machine direction means that asmaller elongation is required before the fibers are close enough to thecross direction to experience tension. Tension, when applied, causes thefibers to try to straighten themselves out and re-orient into the crossmachine direction. If the web were not previously needle punched, thematerial would probably lose all cohesion at this point. However, theneedle punching of the web causes fibers from different layers withdifferent orientations to entangle one another. Because of theseentanglements, the fibers cannot straighten. As cross machine tension isapplied the entanglements tend to bunch together to generate knots thatresemble “spiders” as they have a core with many taught legs emanatingfrom the core in different directions. Each spider forms at a pointwhere a needle caused an entanglement of multiple fibers, which tried topull apart during the cross direction stretch. The bunching of theentanglements gives them the spider like appearance. Each loop of thefuzzy side corresponds to a point where a needle was punched through;consequently, after the cross direction stretch each fuzzy side looplies at the center of a corresponding spider-like knot. This was seen inone experiment where the functional loops (i.e., the outer region of thefuzzy side) of the product were colored purple. All of the purple in thecolored product was visible at the centers of the spiders formed at thebases of the loops. On the other hand, when the non-fuzzy side of thefabric was colored, no gathering of color at the center of the spiderswas observed. Only the fuzzy side, functional loops corresponded toneedle punches, and only these loops were observed to have spiders formaround them. It is believed that the presence of the loop and itscorresponding entanglement is largely responsible for the formation ofthe spider or knot. The fact that a loop is pulled through the web meansthat there is now a vertical fiber (i.e., a fiber extending out of theplane of the web) around which the horizontal fibers of the webentangle. Thus most loops in the finished loop tape have a spider attheir base, which provides increased strength for anchoring the loop.

Stretching the experimental, purple-looped sample past the point atwhich the loops are of maximum height tended to draw the purple tintedloops back into the plane of the web. The greater the stretching, thesmaller the loops grew, until finally they began to pull out of theirentanglements. As this happened, the spider that had formed around themdisappeared and the entangled fibers straightened and sank back into theweb. With increased stretching, after many loops are drawn back andtheir entanglements vanish, the material loses its cohesion, the fibersslide past one another, and the material parts.

From this examination, it appeared that the material is stronger in thecross machine direction, attributed to the fact that the carded fabricis cross-lapped at an angle closer to this direction. By changing thecarding angle progressively away from the cross-machine direction, morestrength in the machine direction should be achievable. Also, machinedirection stretching tends to re-orient the fibers towards the machinedirection. However, since they begin close to cross direction, the mere30 percent elongation that the material undergoes in the above-describedlongitudinal stretching is insufficient to place enough tension on thefibers to straighten them or to cause spiders or knots to form. However,machine direction stretching is considered important for highlycross-directional crosslapped batts, which would otherwise have a laywhich is too cross-directional for a uniform cross direction stretch tobe achieved; in that case the fibers are so close to cross-directionalthat they do not entangle as significantly, nor are they properly spacedin the final product. Instead, they remain very near to each other andnearly parallel. When the spiders do form in such instances, they areelongated in the cross direction and very close together, and the endmaterial is much more dense.

Because in the above-described embodiment the fibers are already morecross-directional than machine-directional, and because the crossdirection stretch applied is greater, the fibers are placed undertension during cross direction elongation. Fibers entangled duringneedle punching tend to clump together, and as the fibers tend tostraighten, these entanglements form spider-like radial patterns offibers.

It was also noted that spiders form at the location of functional loopscreated by deep needle punching, the fibers of which have been drawnthrough some or all of the web. Consequently, the loop fibers entanglethe other fibers and form spiders. This means that in the finishedproduct, the loops have spiders at their base, locking the loop fibersinto the web.

Another way of saying this is that the “loop trees” (see FIG. 3B), whichdo not distinctly appear in the pre-stretched batt, obtain their finalform as fibers of the ground portion of the web are pulled and theentanglements beneath them are tightened during stretching to formknots. As the batt is stretched, the tension in the taut fibers of theweb forces some of the loop trees to stand erect, such that the overallthickness of the stretched batt (with functional loops) can actually begreater than the unstretched batt. To extend the horticultural analogy,the homogeneous thicket of the loop surface of the unstretched battbecomes the orchard of spaced clusters of the stretched product.Although the loop trees or loop formations correspond to locations wherethe batt was punched during super-needling, the resulting “orchard” ofloop formations does not exhibit the same ordered pattern, after the webis stretched, as might be anticipated by the pattern of punches of theneedling process. We believe that the arrangement of loop formations israndomized during the stretching process, as distances betweenentanglements change as a function of the properties, direction andnumber of the fibers connecting various nodes. The resulting product hasno apparent order to the arrangement of loops extending from itssurface.

Despite the relatively wide loop spacing that is achieved, the loops,after curing of the binder, are found to be so strongly anchored and soavailable for engagement by the hooks, that a web unusually treatedaccording to these techniques can perform in an excellent manner despitehaving a gossamer appearance.

Referring back to FIG. 12, while the stretched batt is held on framerails 206 in its stretched condition it is passed through an oven 208 inwhich the product is heated to dry and cross-link acrylic binder 192 andstabilize the dimensional integrity of the batt. Oven 208 is essentiallya convection drier with air venturi nozzles which blow hot air up intoand down onto the web to evaporate some of the water of the adhesive. Inthis example, the heating time and temperature are about one minute and375 degrees F (190 degrees C), respectively. In some embodiments (notshown), the batt is retained on frame rails 206 for secondary coatingpasses through additional coating stations and drying ovens, therebybuilding up a desired laminate structure for particular applications.

In another embodiment, hook-engageable loops are formed on both sides ofthe web by needling, by the super-needling techniques acting on staplefibers that have been described, or by other known techniques. Afterforming the loops the web is passed through a bath of binder. In somecases, where the loops are relatively stiff and the binder is ofsuitably low viscosity, after removal from the bath the binder drainsfrom the loops and the loops, by their own resiliency and stiffnessresume their free-standing stance while capillary action retain thebinder in the center of the fabric. The web is then subjected tostretching and curing as above.

In other instances, as where the loop material is less stiff, auxiliarymeans are employed to remove excess binder after passing through thebath, as by passing the fabric through a nip of squeeze rolls, or bysubjecting both sides of the fabric to an air knife, or by blottingfollowed, in each case for instance by blowing air or otherwiseloosening the loops and causing them to stand upright.

Other embodiments carrying hook-engageable loops on one or both sides,and incorporating heat-fusible binder fibers or other heat-fusiblebinding constituents, are bonded by non-contact means such as by blastsof hot air directed at both sides of the fabric at temperaturessufficient to melt the heat-fusible binding material and lock the fabricstructure in its stretched condition.

Heat fusible fibers or other material colored black or otherwise adaptedto absorb radiant heat, may be activated by radiant heaters to bind theground portion of the fabric following stretching. Care must be taken,in such instances, to avoid mitigation of the engagement properties ofthe free-standing loops.

Referring back to FIG. 12, the stretched batt exits oven 208 stillattached to the pins, and is then pulled from the pins by a de-pinningdevice 210 and a pair of drive rolls 212. The finished, wide batt isthen slit, if desired, into appropriate multiple widths by a slitter 214and spooled on a driven surface winder 216. A dancer 218 between driverolls 212 and slitter 214 monitors the tension in the batt to controlthe speed of winder 216. Slitter 214 can also be used to trim off theedges of the batt that include the material outboard of the frame railsthrough the tenter frame. Optionally, the finished batt can be brushedbefore or after spooling to disentangle loosely-held loop fibers toimprove the consistency of the closure performance between the first andsubsequent engagements with a hook product.

Alternatively, heated rolls, “hot cans” or platens may be employed tostabilize the back side of the fabric in its stretched condition. Thisembodiment does not require a coating or adhesive when usingthermoplastic fibers, as the fibers are locally fused together by heat.Cooled rolls engage the loop side of the fabric during stabilization, toprevent damage to the hook-engageable loops.

It will be understood that the above-described stretching technique canbe employed to advantage on other stretchable, loop-defining non-wovenwebs. Thus, in its broadest aspects, the invention is not to be limitedto the use of needled webs. Webs formed by hydro or air currententanglement can, for instance, be employed.

FIGS. 13 and 13A illustrate a method of forming an entangled, stretchedweb from a spun fiber mat. A continuous base fiber 410 is spun onto asupporting surface between tenter frame rails 412, forming overlappingcoils of spun fiber that drape over each other and about the pins 414 ofthe tenter frame. Base fiber 410 is spun from molten resin from one ormore rotating or oscillating nozzles 432 above the tenter frame, andallowed to fall loose to the tenter frame, such that in its spun andlaid state the fiber is not in tension. The base fiber is sufficientlysoft at this point in the process that overlapping layers of coils aredraped into one another, with portions of upper coils at a lowerelevation than portions of adjacent coils. A useful analogy forvisualizing the mass of coils so draped is to consider a single lengthof rope randomly and loosely draped in overlapping coils onto a levelsurface. Some of the coils at the edges of the mat of fiber so formedencircle pins 414 of the tenter frame rails. Preferably, at least onebase fiber 410 extends the full width of the tenter frame, encirclingpins 414 on both sides. The base fiber (or fibers) will primarily formthe stretched base of the final product, from which the loop formationsextend.

Either during the lay-down of base fiber 410, or immediately thereafter,one or more layers of staple fibers (not shown) are laid upon the mat ofthe base fiber. These fibers may be blown onto the mat, for instance, ina continuous process during the spinning of base fiber 410, such thatstaple fibers are deposited between overlapping portions of base fiber410. In this illustration, the width W₁ of the as-laid fiber mat isabout 36 to 50 inches, and the staple fibers are only about 4 or 5inches in length.

Base fiber 410 is subsequently stretched, preferably in twoperpendicular directions, by pulling its coils which encircle the tenterframe pins 414. The pulling and stretching is accomplished by therelative motions of the tenter frame pins, both in the machine direction(the ratio of D₂ to D₁ is about 1.5:1) and in the transverse direction(W₂ is about 70 to 100 inches), such that the base fiber is pulled inboth directions simultaneously. As the mat is pulled, overlapping coilsof the base fiber 410 (or fibers) slide over one another and becomeentangled with either each other or the staple fibers, forming a randomarray of spaced apart entanglements 416 connected by taut portions 418of base fiber 410. Some portions of base fiber 410 remain slack, but thestretching tightens enough portions of the base fiber to form a planarweb. At a substantial number of entanglements 418 an extending loopstructure (or tree) is formed, consisting primarily of one or morestaple fibers drawn up by the forming entanglement, with an occasionalloop of base fiber 410. The stretched web is thereafter stabilized inits stretched condition by application of a binder (as described above)or by lamination to a supporting material.

In the continuous monofilament base-forming technique illustrated inFIGS. 13 and 13A, it is important that the unstretched batt be soconstructed that a sufficient density of entanglements form uponstretching. In needled batts, entanglements are formed about fiberportions that locally extend perpendicularly to the plane of the batt,having been pushed into and perhaps through the batt by needles.Entanglements can be formed in the continuous monofilament process byseveral mechanisms. For instance, appropriately layering overlappingcoils (or slack sections) of a single base fiber can result in anentanglement upon stretching if top coils are allowed to drape downwithin two or more lower coils. Two or more base fibers can be spun in apattern selected to cause the fibers to cross at several points,creating cross-over points at which the fibers pull against each otherduring stretching. The staple fibers, especially if blown into the battduring the laying of the base fibers, can also form obstructions thatresult in tightenable entanglements upon stretching. In addition, thespun base fibers may be accelerated into the batt in a manner thatcauses portions of the base fibers to assume locally perpendicularorientations, extending into the batt between adjacent fibers.

In most cases where significant strength performance is desired, it ispreferable to employ non-woven materials formed of staple fibers to takeadvantage of their drawn, molecular oriented structure, or other fibersof the substantial tenacity. We have found that loops formed of crimpedstaple fibers work particularly well, as the crimps of the fibers helpto hold the loops apart from each other and exposed for engagement, aswell as permitting greater hook penetration of the “forest” of loopstructures. The crimps can also assist in the formation of the loopstructures, as they form snag points for enhancing the entangling of thebase fibers.

Inter-fiber friction is known to be important for efficient needling.Because of its higher friction, polyester is considered to be a betterfiber material for needling than polyethylene, even though polyethylenecan provide a better hand for some applications. For products tightenedby stretching rather than hyper-needling, however, lower needlingefficiencies can be tolerated, enabling the use of low-friction, goodhand materials like polyethylene.

FIG. 15 shows an enlarged portion of a variable thickness staple fiber422 useful for forming loops. Along its length, the thickness of thefiber undulates to give the fiber an hourglass shape, having alternatingthicker regions 424 and thinner regions 426. These thickness variations,which are exaggerated in the figure for illustration, create snag pointsduring entanglement in a similar fashion as do the crimps of crimpedfibers.

Besides being useful for loop-forming fibers, crimped or variablethickness fibers are also useful for forming the stretched base web. Thecrimps or thickness variations help to entangle base fibers as theyslide against one another during tightening. As known in the art ofneedling, crimps can also improve needling efficiency. In the embodimentillustrated in FIG. 13, the spun base fiber 410 can be effectively“crimped” by subjecting the spun fiber as it leaves its nozzle to aseries of transverse air blasts from one or more directions. Anhourglass thickness variation can be produced in spun fibers bymodulating the ambient air pressure just outside the opening of thenozzle.

As mentioned above, in certain applications the stretched isadvantageously secured to a supporting material in its stretchedcondition. FIG. 16 illustrates a laminate consisting of the stretchedweb 428 formed by one of the processes described above and a layer ofpolyurethane foam 430 flame-laminated to its non-loop surface. Ideally,resin of the foam wicks into the entanglements of the base of the loopmaterial to stabilize the material in its stretched condition. However,a small amount of binder may be added to the base of the web beforebeing introduced to the foam, if necessary to maintain the dimensionalstability of the stretched web prior to lamination. Such a laminatedproduct is useful, for instance, in medical applications such as forstraps and braces which must be loaded directly against the skin. Thefoam provides necessary comfort, while the loop material providesfastener hook engageability.

Other features and advantages of the invention will be realized, and arewithin the scope of the following claims.

What is claimed is:
 1. A method of forming a loop fastener component,the method comprising the steps of providing a sheet-form mat of fibers,the mat having width and including at least one base fiber of a lengthgreater than the width of the mat, and loop fibers freely disposedwithin the mat; tensioning the base fiber by applying tension across thewidth of the mat, thus forming a tensioned web formed by discrete, tautportions of base fiber extending between tightened entanglements,relative movement between portions of the base fiber during tensioningdrawing together portions of the loop fibers to form clusters ofupstanding, hook-engageable loops extending from the tightenedentanglements within the tensioned web; and stabilizing the web in itstensioned state, the stabilized web and loops having a combined weightof less than about 4 ounces per square yard.
 2. The method of claim 1wherein the step of stabilizing includes solidifying a binder within thetightened entanglements of the tensioned web.
 3. The method of claim 1wherein the step of tensioning increases the width of the mat by atleast 20 percent.
 4. The method of claim 1 wherein the step of providinga sheet-form mat of fibers includes continuously spinning the base fiberonto a supporting surface in a predetermined, overlapping pattern. 5.The method of claim 4 further comprising impinging a pulsating air jetagainst the base fiber under conditions which cause the fiber to assumea crimped form as it is spun.
 6. The method of claim 1 in which the basefiber has a cross-sectional property that varies along its length.
 7. Amethod of forming a loop fastener component for hook-and-loop fasteningfrom a generally planar non-woven batt of entangled fibers, the methodcomprising stretching the batt by at least 20 percent in at least onedirection in its plane in a manner to produce a stretched web of weightless than about 4 ounces per square yard and having a generally planarweb body with clusters of hook-engageable loops extending therefrom, asubstantial number of fibers of the body being regionally taut in theplane of the web body, and extending in different directions radiatingfrom tightened fiber entanglements at bases of said clusters of loops;and stabilizing the web in its stretched condition.
 8. The method ofclaim 7 wherein the batt is retained against shrinking in aperpendicular direction within its plane during stretching.
 9. Themethod of claim 8 further comprising, after stretching the batt in saidone direction, stretching the batt by at least 20% in said perpendiculardirection.
 10. The method of claim 7 further comprising, whilestretching the batt in said one direction, stretching the batt by atleast 20% in a second direction perpendicular to said one direction andwithin the plane of the batt.
 11. The method of claim 7 wherein thestretching increases the area of the batt by at least 50%.
 12. Themethod of claim 11 wherein the batt is stretched in a manner that theloop-forming fibers form free-standing formations that extend from theplane of the web body, each formation containing multiple fibers andforming multiple, hook-engageable loops.
 13. A method of forming a loopfastener component for hook-and-loop fastening, the method comprisingproviding a generally planar length of non-woven batt of entangledfibers, the batt having a thickness that varies across its width fromone longitudinal edge thereof to an opposite longitudinal edge thereof;stretching the batt widthwise, thus increasing the width of the batt byat least about 20 percent and producing a stretched web having agenerally planar web body with clusters of hook-engageable loopsextending therefrom, a substantial number of fibers of the body beingregionally taut in the plane of the web body, and extending in differentdirections radiating from tightened fiber entanglements at the bases ofsaid clusters of loops, the step of stretching causing the thickness ofthe batt to become substantially uniform over its width; and thenstabilizing the web in its stretched condition.
 14. The method of claim13 wherein the stretched batt has weight less than about 4 ounces persquare yard.
 15. The method of claim 13 wherein the stretched batt haswidth at least about twice the width of the batt prior to stretching.